1. Field of the Invention
The present invention relates to a sheet punching device for cutting a hole in a sheet, and an image forming apparatus, such as a copying machine, a printer, a facsimile machine, and a composite apparatus including the foregoing devices, provided with the sheet punching device.
2. Related Background Art
Up to now, a sheet punching device includes punches and dies of the number corresponding to the number of holes to be cut in a sheet and cuts the holes in the sheet while the punches are entering die holes, respectively.
However, the conventional sheet punching device is equipped with only the combination of the paired punches and dies of the same number as that of the holes to be cut in the sheet. For that reason, because the punches and the dies are quickly worn, the punches and the dies must be frequently replaced by new ones, resulting in a low efficiency of punching the sheet.
Also, because the number of holes to be cut in the sheet is different depending on the respective countries, if the conventional sheet punching device is adapted to a standard of some countries, it can not be adapted to a standard of other countries.
For example, in Japan, there are many cases in which two holes are cut in the sheet, and the sheet punching device that cuts two holes in the sheet cannot be adapted to such standard as of U.S.A. in which three holes are cut in the sheet.
Under the above circumstances, the operation of the sheet punching device is suspended and the punches and the dies must be replaced by new ones every time the number of holes is changed, thus degrading the punching efficiency.
Also, since an image forming apparatus with the conventional sheet punching device is low in the punching efficiency of the sheet punching device, the efficiency of forming an image on the sheet is low.
The present invention has been made to solve the above problems with the conventional device, and therefore an object of the present invention is to provide a sheet punching device which has high efficiency in punching and can be rapidly adapted to a change in the number of holes to be cut in the sheet, and an image forming apparatus with that sheet punching device.
In order to achieve the above object, according to the present invention, there is provided a sheet punching device that cuts holes in a sheet while punches are entering die holes, in which a plurality of punch trains along each of which a plurality of punches are aligned on a rotating shaft in parallel with the rotating shaft are disposed in the rotation direction of the rotating shaft, and the die holes are disposed in correspondence with the punches of the punch trains.
In the sheet punching device according to the present invention, the number of the punches is identical in each of a plurality of the punch trains, and the punches are disposed on the same positions in the rotation direction of the rotating shaft in each of the punch trains.
In the sheet punching device according to the present invention, the rotating shaft is rotatable in the same direction, and two punch trains are disposed on the rotating shaft at an angle of about 180xc2x0 with respect to each other in the rotation direction, and the number of punches in each of the punch trains is two.
In the sheet punching device according to the present invention, the number of the punches on the punch trains is different in each of the punch trains.
In the sheet punching device according to the present invention, the rotating shaft is rotatable in the same direction, and two punch trains are disposed on the rotating shaft at an angle of about 180xc2x0 with respect to each other in the rotation direction, and the number of the punches in one of those two punch trains is two, and the number of the punches in the other punch train is three.
According to the present invention, there is provided an image forming apparatus comprising: image forming means for forming an image on a sheet supplied from the sheet stacking means; and one of the above sheet punching devices for cutting a hole in the sheet on which the image has been formed by the image forming means.
In the sheet punching device of the present invention, since a plurality of punch trains along each of which a plurality of punches are aligned on a rotating shaft in parallel with the rotating shaft are disposed in the rotation direction of the rotating shaft, and the die holes are disposed in correspondence with the punches of the punch trains, if the number of punches is identical in each of the punch trains, and the punches are disposed on the same positions in the rotation direction of the rotating shaft in each of the punch trains, the number of combinations of the punches and the dies increases as many as the punch trains, and the abrasion of the punches and the dies is delayed. As a result, it is unnecessary to frequently replace the punches and the dies with new ones so that the efficiency of punching the sheet can be enhanced, as compared with the conventional device.
Also, if the number of punches on one of the punch trains is made different from that on another punch train, even if the number of holes to be cut in the sheet is changed, the number of holes to be cut in the sheet can be made different as many as the number of punch trains so as to be adaptive to various sheets. As a result, it is unnecessary to replace the punches and the dies with punches and dies of other types, and the efficiency of punching the sheet can be enhanced as much.
In the image forming apparatus according to the present invention, since there is provided the sheet punching device high in punching efficiency, the sheet can be conveyed onto the sheet punching device while a speed at which an image is formed on a sheet is accordingly improved, and the image processing efficiency with respect to the sheet is enhanced. The present invention is thus capable of improving the productivity.